Method of converting crank case oil to usable oil



Jan. 26, 1960 y G. Kos'rYREFF 2,922,753

METHOD 0F CONVERTING CRNK CASE OIL T0 USABLE OIL Filed May s, 195e United Sites Pate-nt lVIETHOD OF CONVERTING CRANK CASE OIL TO USABLE OIL Geo e Kostyrelf New York N.Y. assignor ofone-half rg to Irvirig B. Guller: New ,York, N.Y.

Application May 8, 1958, Serial No. 733,955

13 Claims. (Cl. 208-183) The present invention relates to a method of converting crank case oil to usable oil, and more particularly to a methodof removing impurities from used oil such as crank case oil so as to produce a pure oil `which can be used for a variety of different purposes.

Used oil from machinery such as automobile engines and the like, such used oil generally being referred to as crank case oil, constitutes a great waste of our natural resources. Such used oil contains many 4impurities lsuch as Water, dust, lint, metal iilings,^metal oxides, tars, pitch, etc. which prevent fur-ther use of the oil without damage to the engine or the like. Many attempts have been made to develop processes for removing these impurities from the oil in order to obtain an oil which can be reused.r In general it may be stated that all of the processes to date involve such high expenses that it is commercially impractical to purify such used oils, and consequently for the most part such used oils constitute a `great waste.

It is, therefore, a primary object of the present invention to provide a method of converting used oil, i.e. crank case oil, to a usable oil in a manner Which is so inexpensive that it is now commercially practicable to obtain usable oil from such used oil.

It is another object of the present invention to provide a method of converting crank case oil to usable oil whereby the resulting usable oil has properties at least equal to the properties of the original oil before useof the same.

It is still another object of the present invention to provide an inexpensive method of converting crank case oil to usable oil whereby the crank case oil is dehydrated and impurities are removed without resulting in great loss of the good oil of the crank case oil.

Other objects and advantages of the present invention will be apparent from a further reading of the specification and of the appended claims.

With the above objects in view, the present invention mainly comprises a method of converting used .oil to usable oil wherein the used oil is dehydrated by evaporation of the water contained therein, the dehydrated oil is treated with sulfuric acid, the sludge is separated from the clear oil, the clear oil is subjected to treatment with adsorbents with heating and steam, and then filtered to result in the production of pure oil that may be reused for all purposes for which the original oil could be used.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, particularly with respect to complete details as to the method of proceeding, will be best understood from the following description of specific embodiments. The accompanying drawing which constitutes a flow sheet sets forth further details as to the method of the present invention which will herein be described in still greater detail. ,Y

Referring first to the flow sheet it will be seen that a complete method of operation including all stagesforthe Patented Jan. 26, i960 obtention of a final product of superior quality, certain of the stages of which can be omitted while still obtaining a usable iinal product, is set forth.

It will be noted that the flow vsheet outlines the various stages of the process of the present invention. In the following each ofthe stages will be .discussed in greater detail:

DEHYDRATION OF CRANK CASE OIL BY HEAT- ING TO ABOVE BOILING POINT OF WATER BUT BELOW DISTILLATION TEMPERATURE OF OIL FOLLOWED `BY SLIGHT COOLING TO PROMOTE SEPARATION, .AND REPEATING UNTIL OIL IS DEHYDRATED.

The crank case oil is iirst dehydrated by evaporation of the water therefrom. This method of drying not only removes water but also removes benzene. Since the presence of benzene or Water is undesirable with respect to subsequent treatment with sulfuric acid, drying by means of drying agents such as calcium chloride and aluminum chloride without evaporation would not be as satisfactory as drying by evaporation of the Water (which also results in the removal of benzene and other substanceswhich would have a'deleterious effect on the subsequent sulfuric acid treatment).

As indicated above, the temperature used for the dehydration should be as high as possible, e.g. above the boilingpoint of water, in `order to effect the most rapid dehydration possible, time being most important from the standpoint of economy. However, ythe temperature should not beso high as to cause distillation or cracking of the oil.

While it is desirable to carry out such dehydration under vacuum, and as a matter of fact under the lowest possible pressure, in order to separate as much as possible the dehydration temperature from the distillation tem.- perature, the use of vacuum treatment requires increased apparatus costs and increased energy costs. Accordingly, under the preferred embodiment of the present invention the dehydration is carried out at normal pressure. According to this embodimentuthe crank case oil is heated to above the boiling point of water but not above 105 C. Most preferably the heating is to a temperature of 104 C.

In order to promote separation of the water from the oil without blowing away excessive amounts of the oil the crank case oil is heated up to 105 C., preferably up to 104 C. while stirring and then cooled to about 96- l00 C. (preferably 100 C.) Without stirring. In this manner some of the Water remains at the bottom of the container and can be drawn off through a tap located at the bottom of the container. The heating to 105 C. and cooling to C. is repeated several times until the oil is dehydrated. The end of the dehydration is observable when foam no longer appears upon heating lfrom 100 C. to C. (this heating beingcarried out while stirring).

The' number of times of heating to 105 C. and cooling to 100 C. until dehydration depends upon the particular impurities in the oil, e.g. the presence of hygroscopic bodies. Generally repetition of the vtreatement from two to six times is suflicient, repetition for four times being averagefor most crank case oils.

COOLING OF DEHYDRATED OIL During the cooling there is some settling of sludge, and

this may be removed.

MIXING OF PORTIONS OF DEHYDRATED OIL `)VITH SULFURIC ACID AND SETTLING-SUB SEQUENT PORTIONS BEING ADDED TO AL- READY SE'I'TLED PORTIONS The cooled, dehydrated oil is then Ytreatedwith sulfuric acid -to remove impurities in the form of a sludge which can be separated from the clear oil by decantation or by withdrawal of Vthe sludgefronrthe' bottom of the contalner. In either case the sludge must be permitted to settle fully and such settling Vis promoted in accordance with the present invention by a special batch Itreatment of the dehydrated oil with sulfuric acid.

In accordance with this embodiment of the invention a portion only of the cooled, dehydrated oil, e.g. one fth thereof, is thoroughly mixed with the sulfuric acid e.g. for about one hour and this portion is then placed in a container to permit settling offthe sludge. While the sludge'is settling in this portion, aisubsequent portion is thoroughly mixed with sulfuric acid eg. for about one hour. This subsequent portion is then added to the container, containing the already settled portion. It has been found that the already settled mixture of sludge and clear oil. promotes the settling of the subsequently added mixture of sludge and oil.

Although the present invention is not meant to be limited as to any theory of why or how the already settled oil promotes more rapid settling of the subse quently added mixture of vsludge and oil, the following theory is given in the'hope that it will help others to better understand the invention. UponV settling of the oil-sludge mixture the densest portion settles to the bottom and the density of the settled layer progressively decreases from bottom to top. The subsequently added mixture of sludge and oil has a greater density than the upper layer of the already settled oil. Consequently, the heavier portions of the subsequently added mixture (charged with concentrated sulfuric acid) very quickly move towards the bottom of the container. Thus, the second portion which has the same volume as the first portion actually settles more rapidly'than the rst portion. Moreover, the total time of settling ofA the first and second portions is less than would be the time required for settling of the two portions if originally mixed together with the sulfuric acid.

Further batches of the cooled, dehydrated oil are then mixed with the sulfuric acid and each added separately to the already settled oil, each subsequent batch being added only after the previous batch has already settled. Not only is the settling more rapid by proceeding in this manner, but of at least equal importance, the settling is more complete.

The number of batches may vary within wide' limits, the greater the number of batches, the more complete the separation of the sludge from the oil. However, in order to reduce operating time at the start of operation in a plant, the operating time being greater with a larger number of batches at the start of operation because each batch must be thoroughly mixed with the sulfuric acid for the full time, although subsequent treatment time would be reduced, the total number of batches into which the original oil is divided should not be un duly high. For practicalV purposes division into 3-25 batches is suitable, and most preferably the number of batches should be from 5-8.

The cooled, dehydrated oil is treated with highly concentrated sulfuric acid, i.e. sulfuric acid having a concentration of at least 66 Baume. The amount of sulfuric acid may vary between l-l0% by volume of the volume of oil treated. Preferably Athe amount of sulfuric acid varies between l2% by volume.

`The sulfuric acid used in this -treatment should preferably be free of selenium. t

SEPARATION OF'SLUDGE FROM CLEAR OIL r[The sludge is separated from the clear oil drawtro ing oif the sludge at the bottom of the container. If desired the purified oil may be subjected to a second or even a third fractional acid treatment of the type described above, the oil of corlrse being permitted to settle and the sludge being separated between acid treatments. After the first or second acid treatment the oil may be treated with 1-2% of fuming sulfuric acid, e.g. 10% fuming sulfuric acid (10% SOSA-H2804) for about l0- 15 minutes. After settling and the drawing ot of the sludge the oil may be treated with l-2% of fuming sulfuric acid of increasing concentration, e.g. 15-20% fuming sulfuric acid. This method of operation may be used to produce completely decolorized oil.

As stated above, the concentrated sulfuric acid used for the originaljtreatment should be free of selenium. It should also be free of HzSeOa and Mn02. If the sulfuric acid is used in small VAvolume it may contain signicant amounts of chromic acid (which is likely to oxidize alcohols to acids). If large amounts of sulfuric acid are used only very small amounts of chromic acid should be present. v

MIXING OF CLEAR OIL WITH ADSORBENT SUCH AS FULLERS EARTH AND HEATING The clear oil separated from the sludge is mixed with an adsorbent such as coarsely puried, non-acid treated fullers earth. The purpose of the adsorbent is of course to remove impurities and therefore the amount of the adsorbent is not particularly critical. However, in order to facilitate subsequent treatmentand separation of the adsorbentsludge from theliquid the amount of adsorbent is preferably maintained at between 3-6% by weight.,

It is in addition particularly advantageous to use nonacid treated fullers earth as the adsorbent inv order to adsorb all of the free sulfuric acid. The non-acid treated fullers earth when mixed with the acid-treated oil not only removes the free sulfuric'acid, but by reason of adsorption of the free sulfuric acid becomes Aconverted into activated fullers earth. The latter acts upon the remainder of the sludge to remove a portion of the impurities.

Thus, the treatment with non-acid treated fullers earth is further economical in that it replaces two steps which would otherwise be necessary, namely, neutralization by `Washing (with all of the disadvantages resulting therefrom), and treatment with activated fullers earth. In addition to economy the process of the present invention is further advantageous in that after treatment of the oil with non-acid treated fullers earth the oil does not smell, whereas if the acid treated oil were neutralized by washing and then treated with activated fullers earth the oil would still have a bad odor.

However, it is possible to use instead of the non-acid treated fullers earth another adsorbent such as Super Filtrol, bone black, blood charcoal, amorphous carbon, Floridin, frankonite and other hydrosilicates originating by decomposition of hornblendes and augites.` It is also possible to use instead of the above adsorbents activated aluminum (produced by melting aluminum and pouring the liquid molten aluminum into cold water), or another metal which is capable of a substratum amorphous effect.

The use of activated aluminum as an adsorbent is advantageous by reason of the fact that the activated aluminum can be easily reconditioned for further use. However, when activated -aluminum is used special precautions should be taken to avoid explosions during subsequent treatment. Activated aluminum not only adsorbs ketones, aldehydes and carbon (both colloidal yand free) but upon contact with acidsit forms hydrogen. Therefore, when activated aluminum is used care should be taken to remove all of the sludge includingthe activated aluminum from the oil before the oil reaches any distilling drum Where it is subjected to high temperature treatment.

The readily available and inexpensive fullers earth is particularly. Vsyllable for. reasons lof economy Fuller-S I earth ha-ving` the'followin'g'compbsition may be used, for example:

The mixture oftclearoil and adsorbent is heated under constantstirring to a temperature of 130 to 210 C., and vpreferably toa temperature of about 180 C.

COOLING, SE'ITLING AND SEPARATING SLUDGE FROM CLEAR LIQUID vrAfter the thorough mixing and heating of the oil with l'the adsorbent the stirring is stopped and the mixture is 'permitted to vcool and settle. The sludge is then separated lfrom the clear oil by careful drawing off ofthe sludge. The separation of the sludge from the oil may be carried outat -any suitable temperature e.g. from C. to 160 C. In order to minimize heat waste, in view of the fact 'that after this stage the oil is again heated, it is advisable to separate the sludge from the clear oil as soon as possible after settling of this sludge, i.e. while the mixture is still relativelyhot.

.MIXING CLEAR OIL WITH ADSORBENT, AND

HEATING WITH STEAM The now partially puriiied oilis again mixed with an ladsorbent such asSuperFiltrol, preferably in an amount of"1% to 3% by weight, and most preferably about 2% should be used if the previous treatment was carried out with activated aluminum.

Instead of Super Filtrol it is suitable to use Tonsil, kieselguhr, and various other kinds of German clay, or the like.

The mixture of oil and adsorbent is heated under `vacuum with steam injection. The higher the pressure (i.e. the lower degree ofvacuum) the more steam should be used. The pressure during this treatment should be preferably 100 mm. Hg or less, and most'preferably 50 mm. Hg or less. The temperature during this treatment may vary between, preferably 275337.5 C. The amount of steam measured as condensed water is preferably 2 to volumes per each volume of oil, depending upon the temperature and pressure.

As the oil-adsorbent mixture is heated to higher temperaturesthe pressure must be lowered. At a temperature of up toV 220 C. the pressure may be'up to 100 mm. Hg. vAs the temperature is increased up to 275 C. the pressureshould be maintained 'at up to 50 mm. Hg. As the "temperature increases jtherinjection of steamshould also beincreased vand khigher amounts o'f steam -should'be used at'higher pressures. -At-a 'temperature of 20D-'275 C. the'amount-'of steam as condensed water is preferably l0 to' 20volumespe'r Volume of' oil, at`50-100 mm. Hg.

vAt lower tpressures of Vless than 50 mm. `Hg e.g. as

lowas '10 m'rn. Hg for'less, and-at temperatures of -up to "3'37i5' fC. the'amountof injected steam may be2 toil vol-urnesp'er -volume of extracted oil.

At reduced 'pressures of about 10 mm. Hg it isjpossibleto use helium to `substitute for some of the steam. Y"In order to -lowerfexpenses the degree fof vacuum is Vnobmade excessively high,`e.g'.- the pressure may b'e-mainf j jdfstill further greatly'increased from 310 Vto vDiiring'fthis stage of the proceeding the adsorbent'not "'nlyihasan ctionn 1adsorbin'g "impurities, but also in At least 2% by weight of this adsorbent` providing for afcorrect1dispersionfof the introduced steam. Thehigh temperature and vacuum treatment'not 'only'has the effect of removing diluent, but also removes a noticeable amount .of impurities. by distillation. The extracted oil, :particularly ithat fraction obtained at a temperature Aup to 275 C. 4may be used .as a fuel for tractors and ztheilike. I

COOLING, SETTLING -AND SEPARATING SLUDGB FROM CLEAR LIQUID The lheatedimixture `of oil Vand -adsorbent is then cooled. The steam injection is continued -until the mixture starts'fto -becooled to below 220 C. Preferably the steam injection is `,continued until the temperature reaches C. f

At the same time the mixture is permitted to settle and as soon as the settling is sufficiently complete the sludge is drawn off. For reasons of economy, to effect a saving in both time and heat, `it is desirable to draw off the sludge at'a temperature as high as p\ossiblee.g. up to 150 C. Of course, fthe separation ofthe sludge from the clear oil can be-'carried outat lower temperatures, e.g. kas low as 20C.

MIXING CLEAR OIL WITH ADSORBENT AND HEATING (WITHOUT STEAM) The clear oil is then mixed with an adsorbent. is preferred at this stage` of the proceeding to use an adsorbent of rhigh decolorizing properties such as Retro] which is an acid-activated montmorillonite adsorbent. Among Yother suitable adsorbents may be 4mentioned Tonsil, Norite or the like. The yamount lof adsorbent such as Retrol is preferably 1-5%, thelower amount being preferred for reasons of economy. l

The mixture of oil and adsorbent is heated, with thorough stirring, without steam, to a temperature of 130-230 C.

COOLING, SETTLING AND vSEPARATING SLUDGE FROM CLEAR LIQUID OIL The mixture is then cooled and allowed to settle. After settling the sludge is drawn off. lThe sludge may be drawn off at a temperature as high as C. or as low as 5 C. The separation of the sludge from the clear oil may be carried out by drawing off the sludge at the bottom of the container -or by decantation.

FILTERING OIL AND DEODORIZING, IF

' NECESSARY The oil may then be filtered, e.g. using a lter press. The filtered oil may also be deodorized, for example 'by reheating up to 130 C. and preferably up to 105 C., followed by steaming until no odor is apparent. This deodorizing treatment does not affect the quality of the oil.

lBy proceeding in the above described manner, ordinary crankcase oil containing such impurities as heavy organic acids, anhydrides and esters thereof, Oxy-acids, estolides, wax-alcohols, aldehydes, ketones, fats which were added for consistency, kerosene, gasoline, mazout, lanoline and sulfur which are added to the oils'by largerms, detergents, benzene absorbed in cars which do not use the full speed run, water, dust, cotton particles, metal filing,

metal oxides, metals in colloidal state, tars, pitches, carbon (bothcolloidal :and in suspension) etc., are puriiied ent invention is composed of saturated normal chain hydrocarbons which actually prevent engine deterioration in asuperior manner to' new oils. Engine test runs have V shown that reconditioned oils produced according to the present invention do not-'heat motors to the same of the example.

extent as the new oils, whichdndicates that thev 'reconditioned oils of the present .invention no longer contain-constituents. which ycan bei; converted to acid ,constituents. Furthermore, the lubricating properties of the reconditioned oils of the present invention are superior -to new oils.` It is believed that this is due to the fact that the new oils are actually to some'extent purified as they are vused in van engine. Thus, when the oils are reconditioned according to the present invention they have already been purified to some extent by use in an' engine, and accordingly the final reconditioned oil has superior properties.

The following example is given to further illustrate the present invention. The scope of the invention is not, however, meant to be limited tothe specific details Example The oil is then cooled by means of an external cooling means such as ice to a temperature of about C.

4 liters ofthe cooled oil are mixed for one half hour, utilizing a stirrer revolving at 800 revolutions per minute, with 100 grams of 66 Baum sulfuric acid. The stirring is continued for one half hour. The acid treated oil is then drawn off into a settling vessel. 1 1

Anadditional 4 liters of cooled oil are mixed for one half hour inthe same manner as above with 100 grams of 66 Baume sulfuric acid for one half hour. By this 'time the first 4 liters of oil has settled. VThe second 4 liters of oil are added to the first 4 liters of oil in the settling vessel.

The operation is continued until the entire 20 liters has been acid-treated and drawn oif into the settling vessel, the total time being two and one half hours. The acid-treated oil is then permitted to settle yfor an additional six hours and the settled oil is decanted into another vessel.

600 grams of coarsely purified, non-acid treated fullers earth is added and the mixture is heated under constant stirring to a temperature of 180 C., The heating and thestirring are both stopped and the mixture is permitted to settle and cool. By the time the temperature reaches 140 C. the mixture is settled suiiiciently to permit dei canting of the supernatent clear oil.

The clear oil is mixed with 200 grams of Super Filtrol and in a steam injection vacuum apparatus heated at a n pressure of 50 mm. Hg to a temperature of 310 C., the

amount of steam introduced during this heating amount- -ing to 40 liters of water. The heating is stopped and the steamed, heated to 110 C. and passed through a lter PTC'SS- 16 liters of clear oilV having properties equivalent to fresh oil are obtained. The oil may be used in cars as a motoroil of superior quality. Y

Without further analysis, the: foregoing will so Afully reveal the gist vof the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the` Letters Patentis:

standpoint fof prior art; fairly .constitute essential characterstics of the generic or specific aspects of thisinvention j and,V therefore, such adaptations should and are intended 1. Amethod of producing usableloilfromiusedoil,

comprising the steps of heating usedoilat a temperature ,above the boiling point of waterand below the distillation temperature of theoil so as to dehydrate said oil;

cooling said dehydrated oil; mixing a first portion of `said dehydrated,.cooled oil with sulfuric` acid so as to rform of said first portion, a mixture'of oil` and a sludge containing impurities; permitting the thus formedmixture to settlei successively mixing further portions of saiddehydrated, cooled oil with sulfuric acid and successively adding the thus formed furtherportions of oil and sludge to said rst portion until the wholefof said yoiihas been mixed with sulfuric acid and added tolsaidrst portion, the already settled portions promoting the. settling ofsubsequently added portion; permitting the thus formed inixture to settle; separating said sludge 'fromr said oil; treating the thus obtained oil by mixing" they samel-withl'anadsorbent and heating so as to cause adsorption1 .of ,impurities by said adsorbent, thereby forming amixtureof clear oil and sludge; and separating said sludgefrom said clear oil, thereby obtaining a clear oil of high quality.` p

2. A method of producing usable 'oilirom used oil, comprising the steps of heating used oil at a temperature above the boiling point of water and below the distilla tion temperature of the oil so as to dehydrate said oil; cooling ysaid dehydrated oil;jmixing aliirst portion consisting of one-third to one twenty-ifth-'of'the lwhole': of

said dehydrated, cooled oil with'sulfuric ac id so as ,to form of said iirst portion a mixture of oil and a sludge containing impurities; permitting thethus formedrmixture to settle;-successively mixing further portions of .said dehydrated, cooled oil with sulfuric acid and successively adding the thus formed further portions of oil and sludge to said first portion until the whole of said oil has been mixed with sulfuric acid and added to said iirst portion. the already settled portions promoting the settling of subsequently added portion; permitting the thus formed mixture toesettle; separating said sludge from said oil;` mixing the thus obtained oil with an adsorbent and heating the ,mixture so as to cause adsorption` of impurities by said adsorbent and form a mixture of oil and sludge; permitting said mixture to settle; separating the `thus settled sludge from said oil; mixing the thus obtained oil with an adsorbent so as to form a mixture thereof; heating said mixture in the presence of steam so as to cause adsorption of y impurities by said adsorbent, thereby forming a mixture of clear oil and sludge; and separating said sludge from -said clear cih-thereby obtaining a clear oil of high quality.

3. A method of producing usable oil from used oil, comprising the steps of heating used oilat vatmospheric pressure at a temperature between 1D0-105 C. while agitating; cooling the thus heated oil to a temperature of 96-100 C.; repeating said heating to 10D-105 C. and cooling to 96-100 C. until said oil is dehydrated; cooling said dehydrated oil; treating said dehydrated, cooled oil with sulfuric acid, thereby forming a mixture of oil and a sludge containing impurities; separating said sludge from said oil; treating the thus obtained oil by mixing the same with an adsorbent and heating so as to cause adsorption of impurities bysaid adsorbent, thereby forming a mixture of clear oil and sludge; and separating said sludge from said clear oil, thereby obtaining a clear oil of high quality.

4. A method of producing usable oil from used oil, comprising the steps of heating used oil at atmospheric pressure at a temperature between 10G-105 C. while agitating; cooling the thus heated oil toa temperature of 9,6-100 C.; repeating said heating to 100g-10S' C.

ingenerare and cooling tof96-100C.unti1-said oilisidehydratc'd; cooling Vsaid dehydrated o'il to -a lmaximum temperature of -C'.; treating-said dehydratedycooled oil withfsulfurie acid, thereby forming amixture of oil anda sludge containing impurities; `separating fsaid vsludge from-said oil;\treating the thus obtained oil by mixing-the same with an-adsorbent andheating so as to cause adsorption of impurities by said adsorbent, k'therebyforniing a `mixture of clear oiland sludge; and separating-'said vs ludge from said clear oil, thereby'obtairiinga-elear oil of high quality.

-5. A method of producing usable-oil-ffroxn used oil, comprising the steps ofheatingusedfoil'at atmospheric pressure at a temperature between 40G-'105 lC. .while agitating; cooling the thus heated oileto :a temperature of 96-100 C.; repeating-said heating to l`00-`10'5-C. and cooling to 96-100 C. until 'said oil isdehydrated; cooling said dehydrated oil toa maximumtemperature of 10 C.; mixing a first portion of said dehydrated, cooled koil v with sulfuric acid so as to form of saidfirst-Aportion a mixture of oil and vsludge containing impurities; permitting the ythus formed mixture-to settle; successively mix- `ing further portions of said dehydrated, cooled oil with sulfuric acid and successively adding-the'thus formed y further portions of oil and sludge -to said first'por-tion until thewhole of said oil has been vmixed with sulfuric Vacid and added to 4said first portionythe already settled portions promoting the settling of subsequentlyadded portions; permitting-the thus formed mixture to settle;separating said sludge from said oil; treating the-thus `obtained oil by mixing the same with an `adsorbent andheating so as to cause adsorption kof impurities l'by said adsorbent, thereby forming a mixtureof clear oil andsludge; and separating said'sludge'from said clear'oil, thereby obtaining a clear oil ofhigh Quality.

6. A method of producing usable oil from Iused oil, comprising the steps of heating used oil `at atmospheric pressure at a temperaturebetween '100-1'05" C. while agitating; cooling the thus heated oil to a--ternperature of 96-100 C., repeating said heating to 10G-105 C. andcooling to 96-100 -C. until said oil is dehydrated; cooling said dehydrated'oil to a maximum temperature of 10 C.; mixing a first portion consisting of one third to one twenty-fifth of the whole of said'dehydrated, cooled oil with sulfuric acid so as to form of said l'first portion a mixture of oil and sludge containing impurities; permitting the thus formed mixture V'to settle; successively mixing further portions of said dehydrated, 'cooled-oil with sulfuric acid and successively adding'the thus formed further portions ofoil and sludge tosaid vfirst portion until the whole of said oil has been mixed with sulfuric acid and added to said first portion; permitting the thus formed mixture to settle; separating said sludge from said oil; treating the thus obtained oil by mixing the same with an adsorbent and heating so as to cause adsorption of impurities by said adsorbent, Ythereby `forming a'mixture of clear oil and sludge; `and `separatingpsaid sludge from said clear oil, therebyobtaining a clear oil of high4 quality.

`7. A method of producing "usableoil fromusedoil, comprising the steps of heating used oil at atmospheric pressure at a temperature between 10C-105 C. While agitating; ycooling the thus heated oil to a temperature of 96-100 C.; repeating said heating to 100-105" C. and cooling to 96-100 C. until said oil is dehydrated; cooling said dehydrated oil to a maximum temperature of 10 C.; mixing a first portion consisting of one fifth to one eighth of the whole of said dehydrated, cooled oil with sulfuric acid so as to form of said first portion a mixture of oil and sludge containing impurities; permitting the thus formed mixture to settle; successively Amixing further portions of said dehydrated, cooled oil with sulfuric acid and successively adding the thus formed further portions of oil and sludge to said first portion until the whole of said oil has been mixed with sulfuric acid and added to said first portion; permitting the thus `formed mixture fto isettle; separatingsaidifsludge from f said oil; treating the thus'fobtainedfoilf by mixing thelsvavme with -anadsorbent andheatin'g so -asto cause adsorption of impuritiesby said adsorbent, therebyforming'fa-mix ture of clear oil and sludge; andseparating said lsludge from said clear oil, thereby obtaining a clear oilof high quality. y y f f 8. A methodof producing usable oil 'from used oil, comprising the stepsof heating'used-oil at-atmospheric pressure at a temperature between 100-'1'0'51C, while agitating; coolingV the-.thus heated oil to atemperature of `96-100o kC.; repeating Vsaid heating to 100-1.05'` 1C. andcooling to 9'6-100"C. until said-oil is dehydrated; cooling said dehydrated oilto a maximum temperature of 10 C.; mixing arstportionconsisting-'of one fifth to one eighth of the whole of said dehydrated, cooled oil with sulfuric acidK-s'o fasto form'of said first portion -a mixture of oil andsvludge containing impurities`;"-pjer mitting the thus lformed mixture kto rsettle; successively mixing further portions f of said dehydrated, cooled oil with sulfuricacid and successively-adding the thus formed further-portions of oil and sludge 'to said rstlportion until'the wholeof vsaidpil'has been mixed with' sulfuric acidand added tofsaid'first portion; permitting thethus formed `mixture tosettle; :separating said sludge Ifrom said oil; mixing the thus= obtained oil with anadsorbent -so as to form a mixture thereo'fyheating said mixture vsaid clear oil, thereby obtaining a clear oil of high quality.

9. A method of producing usable oil from used'oil, comprising the steps of`heating used oil at atmospheric pressure at a temperature "between 10G-105 C. while agitating; cooling V4the thus heated oil to a temperature of l"96-100 C.; repeating said :heating to'100105"C. and cooling to v96-'100 C. until said oil is dehydrated; cooling said dehydrated oil to a maximum temperature of 10 C.; mixing a first portion consisting of onefifth to oneeighth of the whole of said dehydrated, cooled oil with sulfuric acid so as to form o'f said first portion a mixture of oil and sludge containing impurities; permitting the thus formed-mixtureto settle; I successively mixing furtherportions of said dehydrated,cooled oil with sulfuric acidandv successively adding the thus formed further portions of oil and sludge to said first 4portion until the whole of-said oil yhas kbeen mixed with sulfuric acid and added to `said first portion; permitting the. thus formed mixture to settle; separating said sludgeufrom said oil; mixing the thus obtained oil with an adsorbent so as to form a mixture thereof; heating said mixture in the presence of steam so as to cause adsorptionof impurities by said adsorbent, thereby vforming'a mixture of oil and sludge; permittingsaid mixture to settle; lseparating the-thus settled sludge from the oil; mixing the thus obtained oil with an adsorbent and heating the thus formed mixture, thereby, forming a mixture of clear oil and sludgeyand separating said sludge from said clearfoil, thereby obtaining a clear oil'of high quality.

10. A method of producing usable oil from used oil, comprising the steps of heating used oil at atmospheric pressure at a temperature between 1D0-105 C. while agitating; cooling the thus heated oil to a temperature of 96-100 C.; repeating said heating to 10G-105 C. and cooling to 96-100 C. until said oil is dehydrated; cooling said dehydrated oil to a maximum temperature of 10 C.; mixing a first portion consisting of one third to one twenty-fifth of the Whole of said dehydrated, cooled oil with sulfuric acid so as to form of said first portion a mixture of oil and sludge containing impurities; permitting the thus formed mixture to settle; successively mixing further portions of said dehydrated, cooled oil with sulfuric acid and successively adding the thus formed further portions of oil and sludge to said first portion until the whole of said oil has been mixed with sulfuric acid and added to -saidatirstfportiong permitting the lthus .fQrmed mixture tosettle;, separatingsaid sludge from Ythe presencewof 'steam soas to cause adsorption of im- ,t

purities by said adsorbent, therebyiorming a mixture of oil and sludge; permitting said mixture to settle;'sepa ratingthe vthus settled sludge from theoil; ymixing the thus obtained oil with an adsorbentY and heating the thus formedmixturethereby forming a mixture of clear oil4 and sludge; separating said sludge from said clear oil,

-thereby obtaining a clear oil ofhigh quality; and subjecting.y the thus obtained clear oil to a` deodorizing treatment.` l

.- 11 method of producing usable oil from used oil,

comprising the steps of heating used oil at atmospheric pressure at a temperaturebetween 100105 C. while agitating; cooling the thus heated oil to a temperature of`96-,100"` C. repeatingfsaiddheating to 100-105,C.

and cooling'to 96-100C. until saidV oil isvdehydtrated; f

cooling said dehydrated oil to a-maximum temperature of '10 C. mixing a first portion of said dehydrated, vcooled oil with sulfuric acid so as to forni of vsaid first portion a mixture of oil and sludge containing impurities; permitting the thus vformed mixture to settle; successively mixing further portions of said dehydrated, Ycooled oil with sulfuric acid and successively adding Vthe thus formed further portions of oil and sludge tosaid tirst portion until the wholeof said oil has been mixed with sulfuric acid and added to said rst portion, Athe already settled portions promoting the settlingof subsequentlyy added portions;lperrnitting the thus formed mixture to settle; separating said sludge from said oil; mixing the thus obtained oil with van adsorbent and heating the mixture -to a temperature of 13G-210 C. so as to cause adsorption of impurities by saidadsorbent, thereby forming a mixture of clear oil and sludge; and separating said sludge from said clear oil, thereby obtaining a clear oil of high quality. I'

12. A method of producing usable oil from used oil,

comprising the steps of heating used oil at atmospheric pressure at a temperature between 100-105 C. while agitating; cooling the thus heated Voil to a temperature of 96-100 C.; repeating said heating to 100-105 C. andy cooling to 96-l00 C. until said oil is dehydrated; cooling said dehydrated oil to a maximum temperature of C. mixing a first portion of saidk dehydrated,

lcooled oil with sulfuric acid so as to form-tof said first portion a mixture of oil and sludge containing impurities;

permitting the thus formed mixture to settle; successively mixing further portions of said dehydrated, cooled oil with sulfuric acid and successively adding the thus formed further portions of oil and sludge to said lirst portion until the whole of said oil has been mixed with sulfuric acid and added to said iirst portion, the already settled portions promoting the settling of subsequently added separating said sludge from-said oil; mixing the thus obtained oil with an adsorbent and heating the mixture portions; permitting the thus formed mixture to settle;

.mixture of clear oilyand sludge;'s,eparating said sludge from said clear oil; mixing the thus separated clear oil with an adsorhent'so-,as tqfor'rn vatnixture thereof; heat- `,ing saidmixture in the presence L of 4steamat a maximum pressure ,of mm. Hg tota temperature of 275-3325u C.- so as to cause adsorption of impurities byv said 'adsorbent, thereby forminga mixture of oil and sludge; permitting said mixture to settle; separating the `thus settled sludge from the oil; mixing the thus obtained oil with an adsorbent and heating the thus formed mixture, thereby forming almixture of clear oil and sludge; and separating saidsludge from said clear oil, thereby obtaining a clear oilofhigh quality. y I

13. -A method of producing usable oil from used oil, comprising the steps of heating used oil at atmospheric pressure at a temperature between 100-105 C. while agitating; cooling the thus heated oil to a temperature of M96400" C.; repeatingsaid heating to 100-105 C. and cooling to 96-100 C. until said oil is dehydrated; cooling said dehydratedoil to a maximum temperature of l0 C. mixing` a first portion of said dehydrated, cooled oil with sulfuric acid so as to Vform of said first portion a mixture Vof oil and sludge containing impurities;

permittingthe thus formedrmixture'to settle; successively acid and `added to saidy first portion, the already settled portions promoting the settling `of subsequently added portions; permittingtthe thus formed mixtureA to settle; separating said s sludge fromA said voil; mixing the thus obtained oil with an adsorbent and heating the mixture to a temperature of 13G-210? C. so as to cause adsorption ofy impurities by said adsorbent, thereby forming a mixture of clear oil and sludge; separating said sludge from said clear oil; mixing the thus separated clear oil with an adsorbent so as to forma mixture thereof; heating said mixture in the presence of steam at a maximum pressure of 100 mm. Hg to a temperature of 275-337.5

C. so as to cause adsorption of impurities by said adt References Cited in the le of this patent UNITED STATES PATENTS 1,564,501 Weir Dec. 8, 1925 1,707,671 Aycocket al nc Apr. 2, 1929 2,563,369 Reiley et al. Aug.v 7, 1951 

1. A METHOD OF PRODUCING USABLE OIL FROM USED OIL, COMPRISING THE STEPS OF HEATING USED OIL AT A TEMPERATURE ABOVE THE BOILING POINT OF WATER AND BELOW THE DISTILLATION TEMPERATURE OF THE OIL SO AS TO DEHYDRATE SAID OIL, COOLING SAID DEHYDRATED OIL, MIXING A FIRST PORTION OF SAID DEHYDRATED, COOLED OIL WITH SULFURIC ACID SO AS TO FORM OF SAID FIRST PORTION, A MIXTURE OF OIL AND SLUDGE CONTAINING IMPURITIES, PERMITTING THE THUS FORMED MIXTURE TO SETTLE, SUCCESSIVELY MIXING FURTHER PORTION OF SAID DEHYDRATED, COOLED OIL WITH SULFURIC ACID AND SUCCESSIVELY ADDING THE THUS FORMED FURTHER PORTIONS OF OIL AND SLUDGE TO SAID FIRST PORTION UNTIL THE WHOLE OF SAID OIL HAD BEEN MIXED WITH SULFURIC ACID AND ADDED TO SAID FIRST PORTION, THE ALREADY SETTLED PORTIONS PROMOTING THE SETTLING OF SUBSEQUENTLY ADDED PORTION, PERMITTING THE THUS FORMED MIXTURE TO SETTLE, SEPARATING SAID SLUDGE FROM SAID OIL, TREATING THE THUS OBTAINED OIL BY MIXING THE SAME WITH AN ADSORBENT AND HEATING SO AS TO CAUSE ADSORPTION OF IMPURITIES BY SAID ADSORBENT, THEREBY FORMING A MIXTURE OF CLEAR OIL AND SLUDGE, AND SEPARATING SAID SLUDGE FROM SAID CLEAR OIL, THEREBY OBTAINING A CLEAR OIL OF HIGH QUALITY. 